Method of manufacturing a device incorporated substrate and method of manufacturing a printed circuit board

ABSTRACT

A method of manufacturing a device-incorporated substrate as well as a printed circuit board. A transfer sheet is formed having a structure that includes two layers, a metal base material and a dissolvee metal layer and a conductor pattern is formed on the dissolvee metal layer by electroplating. After the transfer sheet on which the conductor pattern is formed is adhered onto an insulating base material, the transfer sheet is removed by separating the metal base material from the dissolvee metal layer and thereafter selectively dissolving and removing the dissolvee metal layer with respect to the conductor pattern.

The subject matter of application Ser. No. 10/523,331, is incorporatedherein by reference. The present application is a Divisional of U.S.Ser. No. 10/523,331, filed Nov. 7, 2005, which is a 371 U.S. NationalStage filing of PCT application PCT/JP2003/007872, filed Jun. 20, 2003,which claims priority to Japanese Patent Application Number JP2002-223846 filed Jul. 31, 2002. The present application claims priorityto these previously filed applications.

TECHNICAL FIELD

The present invention relates to a device-incorporated substrate and amethod of manufacturing a device-incorporated substrate, as well as to aprinted circuit board and a method of manufacturing a printed circuitboard in which the formation of a conductor pattern is performed througha transfer method using a transfer sheet. More specifically, the presentinvention relates to a device-incorporated substrate and a method ofmanufacturing a device-incorporated substrate, as well as to a printedcircuit board and a method of manufacturing a printed circuit board thatare superior in terms of dimensional stability and through which afine-pitch conductor pattern can be formed.

BACKGROUND ART

In recent years, with the increasing reduction in size and the advancein functionality of electronic devices, such as mobile phones, PDAs(Personal Digital Assistants), laptop PCs and the like, high-densitypackaging of electronic components used in them is becoming essential.Conventionally, high-density packaging of electronic components has beenachieved by making component terminals more fine-pitched as a result ofmaking electronic components smaller, by making the conductor pattern ona printed circuit board on which electronic components are mountedfiner, and so forth.

In addition, in recent years, the development of multi-layer printedcircuit boards which make three-dimensional wiring possible by layeringprinted circuit boards is being advanced, and further, the developmentof device-incorporated substrates that aim to further improve packagingefficiency by having electronic components, such as chip resistors, chipcapacitors and the like, and electric devices, such as semiconductorchips and the like, built into these multilayer printed circuit boardsis also being advanced.

As a method of forming a conductor pattern for a printed circuit board,a transfer method using a transfer sheet is conventionally known. Theprocess of manufacturing a printed circuit board using this transfermethod includes, mainly, a pattern formation step for forming aconductor pattern on one surface of a transfer sheet, and a patterntransfer step for removing the transfer sheet after the transfer sheethas been adhered to an insulation layer with the formed conductorpattern in between.

A printed circuit board produced through a transfer method can be easilymulti-layered by forming, in desired places of the insulation layer,via-holes for connecting the layers.

As conventional art of this sort, for example in Japanese Patent No.3051700, a method of manufacturing a device-incorporated substrate usinga transfer method is disclosed. Hereinafter, a conventional method ofmanufacturing a device-incorporated substrate will be described withreference to FIG. 13A through FIG. 13F.

FIG. 13A through FIG. 13F are stepwise sectional views showing aconventional method of manufacturing a device-incorporated substrate. Avoid section 32 for housing a semiconductor chip 36 and via-holeconductors 33 for connecting layers and which are made by fillingthrough-holes with a conductive paste are each formed in an insulatingbase material 31 (FIG. 13A). On the other hand, on one side of atransfer sheet 34 is formed a conductor pattern 35 to be transferredonto the insulating base material 31 (FIG. 13B).

Here, the insulating base material 31 is comprised of a thermo-settingresin that is partially cured, and the transfer sheet 34 is comprised ofa resin film of polyethylene terephthalate (PET) or the like. Inaddition, the conductor pattern 35 is formed by performing patternetching on a conductor foil, such as a copper foil or the like, that isadhered to the transfer sheet 34 in advance.

Next, the semiconductor chip 36 is bonded to a predetermined position ofthe conductor pattern 35 formed on the transfer sheet 34 (FIG. 13C).Then, the upper surface of the insulating base material 31 and the sideof the transfer sheet 34 on which there is the conductor pattern 35 arepressure bonded and the semiconductor chip 36 is housed inside the voidsection 32, while the conductor pattern 35 is connected with thevia-hole conductors 33 (FIG. 13D). The conductor pattern is buried inthe upper surface of the partially cured insulating base material 31,and thereafter, just the transfer sheet 34 is removed from theinsulating base material 31. Then, by completely curing the basematerial 31 through a heat treatment, a device-incorporated substrate 30is obtained (FIG. 13E).

In addition, as shown in FIG. 13F, by layering insulating base materials39 and 40 on which conductor patterns 37 and 38, respectively, areformed through a method similar to the one above onto theabove-mentioned device-incorporated substrate 30, a multi-layeredprinted circuit board 41 is obtained.

However, in this conventional method of manufacturing adevice-incorporated substrate, because the transfer sheet 34 iscomprised chiefly of a resin film, there is a problem in that due tostretching and warpage in the transfer sheet 34 caused during handling,errors in the pattern configuration of the conductor pattern 35 to betransferred occur with greater likelihood. Therefore, with thisconventional method of manufacturing a device-incorporated substrate, itis extremely difficult to accommodate the trend towards finer (morefine-pitched) conductor patterns, which is to progress further in thefuture.

In addition, the conductor pattern 35 formed on the transfer sheet 34 isformed, as disclosed in Japanese Patent Application Publication No. HEI9-270578 for example, by pattern etching a metal foil adhered onto thetransfer sheet 34, or, as disclosed in Japanese Patent ApplicationPublication No. HEI 10-335787 for example, by pattern etching a metallayer that is formed on the transfer sheet 34 directly throughsputtering or the like. As the method of etching, wet etching isadopted.

In other words, in the conventional method of manufacturing adevice-incorporated substrate, because wet etching is used in theformation of the conductor pattern 35, there is a problem which is that,in the future, it is going to become difficult to form fine-pitchpatterns with high precision.

On the other hand, it is also conceivable to have the transfer sheet bemade of a metal material such as stainless steel or the like. In thiscase, because the rigidity is higher as compared to a case where thetransfer sheet is made of a resin film, the dimensional stability of theconductor pattern is improved. However, in this case, there is a problemin that if the rigidity of the insulating base material, which is thetransfer target, is high, it becomes difficult to remove the transfersheet from the insulating base material and the transfer operation forthe conductor pattern cannot be performed properly.

The present invention is made in view of the problems above, and makesit an issue to provide a device-incorporated substrate and a method formanufacturing a device-incorporated substrate, as well as to a printedcircuit board and a method of manufacturing a printed circuit board inwhich the dimensional stability of the conductor pattern is secured tomake it possible to form a fine-pitch conductor pattern on an insulatinglayer with high precision and in which the removal of the transfer sheetcan be performed properly.

DISCLOSURE OF THE INVENTION

In solving the issues above, in the present invention, by making thetransfer sheet metallic and giving the transfer sheet electricalconductivity, forming a fine-pitch conductor pattern with high precisionis made possible using a pattern plating technique by an additivemethod.

When transferring the formed conductor pattern to the insulating layer,the transfer sheet is removed from the insulating layer after thetransfer sheet and the insulating layer have been adhered to each other.In the present invention, because the transfer sheet is comprisedchiefly of a metal material, there is hardly any dimensional changeduring handling, and thus, the dimensional stability of the conductorpattern to be transferred is secured.

In addition, in the present invention, the removal of the transfer sheetfrom the insulating layer is done mainly by dissolving and removing thetransfer sheet. Thus, even in cases where the insulating layer, which isthe transfer target, has strong rigidity, it is possible to ensure aproper transfer operation for the conductor pattern.

Here, the transfer sheet may be so configured to include a metal basematerial, and a dissolvee metal layer that is layered so as to beseparable with respect to the metal base material and onto which aconductor pattern is formed. The metal base material accounts for themain portion of the entire thickness of the transfer sheet, and is somade that it has, mainly, mechanical properties or material propertieswhich are essential at the time of handling. When such a metal basematerial is separated and removed from the dissolvee metal layer, thedissolvee metal layer, which is part of the transfer sheet, remains onthe conductor pattern that has been transferred onto the insulatinglayer. As such, by dissolving and removing this dissolvee metal layer,of the transfer sheet is completely removed from the insulating layer.In such a case, since the time required for the dissolution and removalof the transfer sheet can be shortened, the removal process for thetransfer sheet is simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view that shows, schematically, the configurationof a device-incorporated substrate according to a first embodiment ofthe present invention;

FIG. 2 is a sectional view showing a state where the device-incorporatedsubstrate shown in FIG. 1 has been multi-layered;

FIGS. 3(A) through (H) are stepwise sectional views illustrating amethod of manufacturing a device-incorporated substrate according to thefirst embodiment of the present invention, where (A) through (C) show avoid section forming step, (D) through (G) show a pattern forming step,and (H) shows part of a pattern transfer step;

FIG. 4A through FIG. 4D are stepwise sectional views illustrating amethod of manufacturing a device-incorporated substrate according to thefirst embodiment of the present invention, where FIG. 4A shows a devicehousing step, and FIG. 4B through FIG. 4D show a step for removing atransfer sheet;

FIG. 5A is a sectional view that shows, schematically, the configurationof a transfer sheet applied in the first embodiment of the presentinvention, and FIG. 5B through FIG. 5D are sectional views illustratingmodifications thereof;

FIG. 6 is a flow chart illustrating a method of manufacturing adevice-incorporated substrate according to the first embodiment of thepresent invention;

FIGS. 7(A) through (G) are stepwise sectional views illustrating amethod of manufacturing a printed circuit board according to a secondembodiment of the present invention, where, in particular, (C) through(F) show a pattern forming step, and (G) shows part of a patterntransfer step;

FIG. 8A through FIG. 8C are stepwise sectional views illustrating amethod of manufacturing a printed circuit board according to the secondembodiment of the present invention, and, in particular, show a removalprocess for a transfer sheet;

FIGS. 9(A) through (H) are stepwise sectional views illustrating amethod of manufacturing a device-incorporated substrate according to athird embodiment of the present invention;

FIG. 10A through FIG. 10D are stepwise sectional views illustrating amethod of manufacturing a device-incorporated substrate according to thethird embodiment of the present invention;

FIG. 11A through FIG. 11F are stepwise sectional views illustrating amethod of manufacturing a device-incorporated substrate according to afourth embodiment of the present invention;

FIG. 12 is a sectional view of a main portion illustrating amodification of a chip mounting step of the first embodiment of thepresent invention; and

FIG. 13A through FIG. 13F are stepwise sectional views illustrating aconventional method of manufacturing a device-incorporated substrate.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, each embodiment of the present invention is described withreference to the drawings.

First Embodiment

FIG. 1 through FIG. 5D show the configuration of a device-incorporatedsubstrate 50 according to the first embodiment of the present invention.An insulating base material 51, which constitutes an insulating layer,has formed therein a void section 52 for housing a semiconductor chip 56as an electric device, and through-holes 53, 53 for connecting the frontand back sides of the insulating base material 51. The through-holes 53,53 are filled with an electrically conductive material 59, such assolder and the like.

In the present embodiment, the insulating base material is comprised ofa resin base material of mainly a thermoplastic resin material, however,it is not limited thereto, and may be selected as deemed appropriatedepending on the application or usage. For example, glass fiberimpregnated with epoxy resin, glass fiber impregnated with polyimideresin, or paper impregnated with phenol resin or the like may be used.In addition, bismaleimide triazine resin, benzo-cyclo-butene resin,liquid crystal polymers and the like may also be used.

For the electrically conductive material 59 that the through-holes 53are filled with, either a leaded or non-leaded solder material may beused, but from an ecological point of view, it is preferable that anon-leaded solder material be used. As non-leaded solder materials,alloys of Sn—Ag to which Bi, In, Cu, Sb and the like are added are wellknown. In addition, as electrically conductive materials other thansolder materials, an electrically conductive paste that is obtained bymixing electrically conductive particles, such as silver powder, copperpowder and the like, in resin may be used, for example.

On the surface of the insulating base material 51, there is provided anelectrically non-conductive adhesive 54, and a conductor pattern 55 thathas been patterned to a predetermined configuration is adhered onto thisadhesive 54. The conductor pattern 55 is comprised of, for example, anelectroplated film of copper, and is electrically bonded to thesemiconductor chip 56 housed within the void section 52, while it isalso electrically connected with the electrically conductive material 59inside the through-holes 53. In the present invention, as will bedescribed later, the conductor pattern 55 is formed on the insulatingbase material 51 by a transfer method.

The semiconductor chip 56 in the present embodiment is comprised of abare chip, and gold or gold plated bumps (metal protrusive electrodes)57 are formed on an aluminum electrode pad section provided on itsbonding surface (active surface). In addition, the bumps 57 may be,besides the ball bumps shown in the drawing, stud bumps or plated bumps.Further, instead of semiconductor bare chips, semiconductor packagingcomponents, such as BGA/CSP and the like, in which bumps are formed inrows or within a given area may also be used for the present invention.

Inside the void section 52 and between the conductor pattern 55 and thesemiconductor chip 56 is formed an underfill resin layer 58 comprised ofthermosetting adhesive resin, such as epoxy resin and the like, forexample. The semiconductor chip 56 maintains its bond with the conductorpattern 55 by virtue of the underfill resin layer 58. In addition, thesemiconductor chip 56 within the void section 52 may also be completelysealed with the same resin material.

The surface side of the conductor pattern 55 is covered with a solderresist 60, but openings 60 a, 60 a are formed in places corresponding tothe through-holes 53, and thus the conductor pattern 55 is exposed.

According to the device-incorporated substrate 50 of the presentembodiment, since the conductor pattern 55 is comprised of anelectroplated layer, it becomes possible to make the conductor pattern55 finer pitched, and thus, it is possible to achieve a furtherimprovement in packaging density.

Next, FIG. 2 shows a device-incorporated multi-layer substrate 65 inwhich a plurality of the device-incorporated substrates 50 configured inthe manner described above are layered. In the present example, aconfiguration where three of the device-incorporated substrates 50 ofthe configuration described above are mounted on a base substrate 66 isshown. The electrical and mechanical connections between the layers inthe device-incorporated multi-layer substrate 65 is achieved through theelectrically conductive material 59 that is bonded to the surface of theconductor pattern 55 via the openings 60 a in the solder resist 60.

In addition, by connecting the layers with the electrically conductivematerial 59 as mentioned above, connections can be made in a shortertime and resistance can be kept lower as compared to a case where anelectrically conductive paste is used.

The base substrate 66 has an insulating base material 67, an upperwiring layer 70 and a lower wiring layer 71 pattern-formed on the frontand back surfaces of the insulating base material 67, and through-holeplating 68 for connecting these wiring layers 70 and 71 formed. Inaddition, the insides of these through-holes are filled with a filler 69of either an electrically conductive material or an electricallynon-conductive material, and thus, the so-called pop-corn phenomenon isprevented and heat dissipation efficiency is improved.

The device-incorporated multi-layer substrate 65 thus configured takeson the configuration of a land grid array (LGA), and when being mountedon a mother board, external electrodes, such as ball bumps and the like,are provided on the lower wiring layer 71 that is exposed via openings73 a, 73 a in a solder resist 73. In addition, some other electricdevice or electric component may further be mounted on the wiring layer(conductor pattern) 55 of the device-incorporated substrate 50 at thetop-most layer.

Next, a method of manufacturing the device-incorporated substrate 50related to the present invention will be described with reference toFIG. 3 through FIG. 6.

First, as shown in FIG. 3(A), the insulating base material 51 of theconfiguration described above is prepared, and the adhesive 54 forforming an adhesive material layer is applied onto the surface thereof(FIG. 3(B)).

The adhesive 54 is there to adhere the conductor pattern 55, which islater transferred, to the insulating base material 51, and it isnecessary that it be electrically non-conductive. In addition, in orderto prevent the adhesive from flowing out into the void section 52 andthe through-holes 53 when the conductor pattern 55 is transferred, amaterial that has low flow and has high shape holding properties is usedfor the adhesive 54. An example of such a material would include, forexample, “AS-3000” produced by Hitachi Chemical Co., Ltd.

Next, as shown in FIG. 3(C), a void section forming step (step S1) forforming the void section 52 for housing a device and the through-holes53 for connecting layers is carried out with respect to the insulatingbase material 51. For example, known drilling processing techniques suchas processes using drills and routers, mold punching, laser processingand the like may be adopted for the forming of the void section 52 andthrough-holes 53, and a plurality of sheets may be processed at once. Inaddition, internal dimensions greater than the outer dimensions of thesemiconductor chip 56 to be housed is required for the void section 52.

Along with the preparation step for the insulating base material 51described above, a step of forming the conductor pattern 55 (step S2) iscarried out as shown in FIGS. 3(D) through (G). In the presentembodiment, in forming the conductor pattern 55, a transfer sheet 61 ofthe configuration shown in FIG. 5A is used.

The transfer sheet 61 has a three-layer structure of a metal basematerial 62 of copper of a thickness of, for example, approximately 100μm, an electrically conductive adhesive resin layer 63, and a dissolveemetal layer 64 of chromium (Cr) of a thickness of, for example, 5 μm orless. The metal base material 62 and the dissolvee metal layer 64 arelayered so as to be mutually separable with the electrically conductiveadhesive resin layer 63 in between.

The metal base material 62 accounts for the main portion of the entirethickness of the transfer sheet 61, and is so made that it has, mainly,mechanical properties or material properties which are essential forhandling. The electrically conductive adhesive resin layer 63 iscomprised of a material that is able to ensure conduction between themetal base material 62 and the dissolvee metal layer 64, and thatenables both to be separated and removed. For example, benzotriazoleresin that is formed in a layer is used. The dissolvee metal layer 64 iscomprised of a metal foil or a metal plating layer, and is made of ametal material that is dissimilar from the conductor pattern 55 so thatit can be selectively etched with respect to the conductor pattern 55.

In addition, configuration examples for separating and removing both themetal base material 62 and the dissolvee metal layer 64 are not limitedto those above, and other configuration examples may also be adopted,details of which will be described later.

Referring to FIG. 3(D), on the surface on the side of the dissolveemetal layer 64 of the transfer sheet 61 of the configuration mentionedabove, a photoresist film 72 is formed. The photoresist film 72 may beeither of a dry film resist and a liquid resist. Then, the photoresistfilm 72 is patterned to a predetermined configuration by performingvarious processes such as exposure and development on the formedphotoresist film 72, thereby forming a plating resist 72A (FIG. 3(E)).

Subsequently, the transfer sheet 61 is immersed into, for example, anelectrolytic bath of copper along with the plating resist 72A and isconnected to a cathode electrode not shown in the drawing, therebydepositing an electroplated layer 55A upon the dissolvee metal layer 64(FIG. 3(F)). Then, after the electroplated layer 55A is formed, theplating resist 72A is removed (FIG. 3(G)). Thus, the conductor pattern55 comprised of the electroplated layer 55A is formed on the surface ofthe transfer sheet 61.

In addition, the electroplated layer 55A is formed not only on thedissolvee metal layer 64 of the transfer sheet 61 but also on the metalbase material 62, however, illustration thereof has been omitted.

In general, compared to a method of forming a conductor pattern byremoving unwanted parts of a conductor layer through wet etching (asubtractive method), a method of forming a conductor pattern bydepositing a conductor layer only in desired places throughelectroplating (an additive method) allows for the formation of finerpatterns. Therefore, according to the present embodiment, fine-pitchconductor patterns with an L/S of, for example, 10 μm/10 μm can beformed with high precision.

In addition, in cases where fine-pitch conductor patterns are notrequired, a conductor pattern may also be formed by further forming aconductor layer, by such methods as electroplating and the like, on thedissolvee metal layer 64, and pattern etching this conductor layer.

Next, as shown in FIG. 3(H), the transfer sheet 61 and the insulatingbase material 51 are adhered to each other with the formed conductorpattern 55 in between, and the conductor pattern 55 is adhered to theadhesive 54 on the insulating base material 51 (step S3).

Here, because the transfer sheet 61 is metallic, it has higher strengthas compared to a conventional transfer sheet made of a resin film, andtherefore, stretching and warpage during handling of the transfer sheet61 are suppressed, and it is possible to adhere the fine-pitch conductorpattern 55 properly onto the insulating base material 51 with highdimensional stability.

In addition, because the transfer sheet 61 can be given sufficientstrength, pattern transfer at higher loads than are conventional becomespossible, and limitations on the transfer process can be reduced. Inparticular, because local deformations in the transfer sheet upontransfer are suppressed, deformation and breaks in the conductor patterncan be prevented.

Subsequently, as shown in FIG. 4A, a step of housing the semiconductorchip 56 within the void section 52 of the insulating base material 51,and of bonding the bumps 57 formed on the active surface of thesemiconductor chip 56 to the conductor pattern 55 is performed (stepS4). The mounting of the semiconductor chip 56 with respect to theconductor pattern 55 is performed using, for example, a known mounterapparatus.

In addition, in the present embodiment, since the bumps 57 are formedwith gold or with gold plating on their surfaces, if they are bondeddirectly to the conductor pattern (copper) 55, it becomes a bond betweenAu—Cu. As such, by further forming a tin (Sn) metal film, throughelectroplating and the like, on the surface of the conductor pattern 55formed on the transfer sheet 61, the bonding step mentioned aboveresults in a bond between Au—Sn, and therefore, as compared to a bondbetween Au—Cu, bonding of the semiconductor chip 56 at lowertemperatures and lower loads becomes possible. Sn metals would includeSn and Sn alloys (SnAg, SnBi, SnCu and the like). In addition, besidesSn metals, similar results can also be achieved by forming a NiP/Aufilm.

On the other hand, instead of forming the bumps 57 of the semiconductorchip 56 with Au, they may be formed with a Sn metal. In such a case, thebumps may be formed solely of a Sn metal, or they may be balls of othermetals or resin balls whose surface is plated with a Sn metal. Sn metalswould include Sn, SnAg, SnBi, SnCu, SnAgCu, SnAgBi, SnAgBiCu, and thelike.

After the semiconductor chip is bonded to the conductor pattern 55, astep of injecting thermosetting resin, such as epoxy, into the voidsection 52, and forming the underfill resin layer 58 between theconductor pattern 55 and the semiconductor chip 56 is performed (FIG.4A, step S5). Thus, the conductor pattern 55 is supported by both thetransfer sheet 61 and the underfill resin layer 58.

Thus, a “device housing step” related to the present invention iscomprised of a step of bonding the semiconductor chip 56 to theconductor pattern 55 and a step of forming the underfill resin layer 58for sealing the bonded semiconductor chip 56 within the void section 52.

In addition, the step of bonding the semiconductor chip 56 is notlimited to the one mentioned above, and the semiconductor chip 56 may bebonded to the conductor pattern 55 on the transfer sheet 61 in advance,and the bonded semiconductor chip 56 may be housed inside the voidsection 52 when the insulating base material 51 and the transfer sheet61 are adhered to each other. In this case, since the transfer sheet 61is metallic, deformation and the like of the transfer sheet 61 due tothe weight of the semiconductor chip 56 itself can be suppressed.

Here, if a substance having adhesive properties is used for the platingresist 72A, it is possible to use the plating resist 72A as an underfillresin layer for the semiconductor chip 56 as shown in FIG. 12, forexample. In this case, the thickness of the conductor pattern 55 needonly be made a length that can be reached by the bumps 57 of thesemiconductor chip 56.

Next, a step of removing the transfer sheet 61 is performed. In thepresent embodiment, the removal of the transfer sheet 61 is comprised ofa step of separating and removing the metal base material 62 from thedissolvee metal layer 64 (FIG. 4B) and a step of dissolving and removingthe dissolvee metal layer 64 (FIG. 4C).

Referring to FIG. 4B, the step of separating and removing the metal basematerial 62 from the dissolvee metal layer 64 is performed by separatingthe metal base material 62 from the dissolvee metal layer 64 via theelectrically conductive adhesive resin layer 63 (step S6).

In addition, in order to have it separate from the dissolvee metal layer64 along with the metal base material 62, the electrically conductiveadhesive resin layer 63 may have a release agent applied in advance on apredetermined area of its surface on the side of the dissolvee metallayer 64.

By adding, at the boundary section between the metal base material 62and the dissolvee metal layer 64 at the edge of the transfer sheet 61, aslit for starting separation, the separation process for the metal basematerial 62 can be performed with ease. In addition, during the processof separating the metal base material 62, since the dissolvee metallayer 64 is supported by the adhesive 54 and the underfill resin layer58 via the conductor pattern 55, it is possible to perform theseparation and removal of the metal base material 62 and the dissolveemetal layer 64 properly (FIG. 4C).

On the other hand, in the step of dissolving and removing the dissolveemetal layer 64, only the dissolvee metal layer 64 is selectively removed(FIG. 4D, step S7) using an etching solution that dissolves thedissolvee metal layer 64 but not the conductor pattern 55. In thepresent embodiment, since the conductor pattern 55 is formed with copperand the dissolvee metal layer 64 with chromium, by using, for example, ahydrochloric etching solution, just the dissolvee metal layer 64 can bedissolved and removed while leaving the conductor pattern 55.

Thus, a “pattern transfer step” in the present embodiment is comprisedof the respective steps from the step of adhering the insulating basematerial 51 and the transfer sheet 61 to each other (step S3) to thestep of dissolving and removing the dissolvee metal layer 64 (step S7).

After the removal of the transfer sheet 61 is completed, an electricalconductor filling step of filling the through-holes 53 of the insulatingbase material 51 with the electrically conductive material 59 as anelectrically conductive material through screen printing or a dispensingmethod is performed as shown in FIG. 1, while a step of covering thesurface of the conductor pattern 55 with the solder resist 60 except forparts corresponding to areas where the through-holes 53 are formed isperformed (step S8). In addition, if the device-incorporated multi-layersubstrate 65 shown in FIG. 2 is to be obtained, a predeterminedmulti-layering process is performed (step S9).

Thus, the device-incorporated substrate 50 of the present embodiment isproduced.

According to the present embodiment, since the transfer sheet 61 is mademetallic, it is possible to form the fine-pitch conductor pattern 55with high precision using a pattern plating technique based on anelectroplating method. In addition, since the transfer sheet 61 haspredetermined mechanical strength and heat resistance, dimensionalchanges during handling or heating is virtually eliminated, and it ispossible to ensure the dimensional stability of the conductor pattern 55that is transferred.

Further, because the removal of the transfer sheet 61 in the patterntransfer step is ultimately performed by way of dissolving throughetching, even in cases where the rigidity of the insulating basematerial 51 is strong, it is possible to ensure an adequate operation oftransferring the conductor pattern 55.

In addition, according to the present embodiment, since the transfersheet 61 is so configured to include the metal base material 62 and thedissolvee metal layer 64 that is layered so as to be separable withrespect to this metal base material 62, and since the removal of thetransfer sheet 61 is comprised of a step of separating and removing themetal base material 62 from the dissolvee metal layer 64 and a step ofdissolving and removing the dissolvee metal layer 64, the removal of thetransfer sheet 61 is made easier, and thus, an improvement inproductivity can be expected.

Second Embodiment

FIG. 7, and FIG. 8A through FIG. 8C show the second embodiment of thepresent invention. In the present embodiment, a method of manufacturinga printed circuit board related to the present invention will bedescribed.

First, as shown in FIG. 7(A), an insulating base material 81 isprepared, and an adhesive 84 for forming an adhesive material layer isapplied onto the surface thereof (FIG. 7(B)). The same materials asthose of the insulating base material 51 and the adhesive 54 describedin the first embodiment above are used for the insulating base material81 and the adhesive 84 of the present embodiment.

On the other hand, a conductor pattern 85 to be transferred onto theinsulating base material 81 is, as in the first embodiment, formed on ametallic transfer sheet 91 through electroplating as shown in FIGS. 7(C)through (F). The transfer sheet 91 has, though not described in detail,a configuration similar to that of the transfer sheet 61 in the firstembodiment, and is comprised of a metal base material 92 of copper, adissolvee metal layer 94 of chromium, and an electrically conductiveadhesive resin layer (illustration omitted) that lies between the two.

On the dissolves metal layer 94 of the transfer sheet 91 is formed aplating resist 73A which is obtained by patterning a solder resist 73,and the conductor pattern 85 is comprised of an electroplated layer(copper) 85A that is deposited in areas marked out by the plating resist73A (FIG. 7(E)). By adhering the transfer sheet 91 on which theconductor pattern 85 is formed onto the insulating base material 81after the plating resist 73A has been removed, the conductor pattern 85is transferred onto the adhesive 84 (FIG. 7(G)).

Subsequently, as shown in FIG. 8A through FIG. 8C, a step of removingthe transfer sheet 91 that has been adhered onto the insulating basematerial 81 is performed. The removal of the transfer sheet 91, as inthe first embodiment, is performed through a step of separating andremoving the metal base material 92 from the dissolvee metal layer 94,and a step of dissolving and removing the dissolvee metal layer 94. Inparticular, for the dissolution and removal of the dissolvee metal layer94, a hydrochloric etchant, for example, that dissolves the dissolveemetal layer (Cr) 94 but not the conductor pattern (Cu) 85 may be used.

A printed circuit board 80 thus produced takes on, as shown in FIG. 8C,a configuration where the conductor pattern 85 formed throughelectroplating is adhered to the adhesive 84 on the insulating basematerial 81.

According to the present embodiment, because the transfer sheet 91 ismade metallic, it is possible to form the fine-pitch conductor pattern85 with high precision using a pattern plating technique based onelectroplating. In addition, since the transfer sheet 91 haspredetermined mechanical strength and heat resistance, dimensionalchange during handling and heating can be virtually eliminated, therebyensuring the dimensional stability of the conductor pattern 85 that istransferred.

Further, because the removal of the transfer sheet 91 in the patterntransfer step is ultimately carried out by dissolution through etching,a proper transfer process of the conductor pattern 85 can be ensuredeven in cases where the rigidity of the insulating base material 81 isstrong.

In addition, according to the present embodiment, since the transfersheet 91 is made to include the metal base material 92 and the dissolveemetal layer 94 that is layered so as to be separable with respect tothis metal base material 92, and since the removal of the transfer sheet91 is comprised of a step of separating and removing the metal basematerial 92 from the dissolvee metal layer 94, and a step of dissolvingand removing the dissolvee metal layer 94, the removal of the transfersheet 91 becomes easier, and thus, an improvement in productivity can beexpected.

Third Embodiment

FIG. 9, and FIG. 10A through FIG. 10D show the third embodiment of thepresent invention. In the present embodiment, a method of manufacturinga device-incorporated substrate related to the present invention will bedescribed. It is to be noted that, in the drawings, the same referencenumerals are given to parts that have correspondence in the firstembodiment described above, and detailed descriptions thereof will beomitted.

First, as shown in FIG. 9(A), an insulating base material 51 isprepared, and an adhesive for forming an adhesive 54 is applied onto thesurface thereof (FIG. 9(B)).

Subsequently, as shown in FIG. 9(C), a void section forming step forforming a void section 52 for housing a device and through-holes 53 forconnecting layers is performed with respect to the insulating basematerial 51.

In conjunction with the preparation step for the insulating basematerial 51, a step of forming a conductor pattern 55 is performed asshown in FIGS. 9(D) through (G).

In the present embodiment, in forming the conductor pattern 55, atransfer sheet 61 of the configuration shown in FIG. 5A is used. Inother words, it is comprised of a metal base material 62 of copper, adissolvee metal layer 64 of chromium, and an electrically conductiveadhesive resin layer that lies between the two (FIG. 9(D)).

The conductor pattern 55 shown in FIG. 9(E) is, as in the firstembodiment described above, comprised of an electroplated layer formedon the surface of the transfer sheet 61 on the side of the dissolveemetal layer 64.

In the present embodiment, a step of burying an insulating film in thegaps in the formed conductor pattern, and of flattening the surface ofthe transfer sheet 61 on the side of the dissolvee metal layer 64 isthen performed.

In this step, first, as shown in FIG. 9(F), an insulating film 87 of aninsulating resin such as epoxy resin, for example, is applied onto theentire surface of the transfer sheet 61 on the side of the dissolveemetal layer 64 from above the formed conductor pattern 55 through ascreen printing method, and is then cured.

Then, as shown in FIG. 9(G), the cured insulating film 87 is buffed, andthe surface of conductor pattern 55 is exposed.

Thus, the insulating film 87 is buried into the gaps of the conductorpattern 55, and the surface of the transfer sheet 61 on the side of thedissolvee metal layer 64 is flattened.

Subsequently, as shown in FIG. 9(H), the transfer sheet 61 and theinsulating base material 51 are adhered to each other with the formedconductor pattern 55 in between, thereby adhering the conductor pattern55 onto the adhesive 54 on the insulating base material 51.

Here, because the transfer sheet 61 is metallic, its strength is higheras compared to a conventional transfer sheet that is comprised of aresin film, and therefore, it is possible to suppress stretching andwarpage of the transfer sheet 61 during handling, and to adhere thefine-pitch conductor pattern 55 properly onto the insulating basematerial 51 with high dimensional stability.

In addition, because sufficient strength can be given to the transfersheet 61, pattern transferring at higher loads than is conventionalbecomes possible, and limitations on the transfer process can bereduced. In particular, because local deformations in the transfer sheetupon transfer are suppressed, deformation and breaks in the conductorpattern can be prevented.

Further, because the surface of the transfer sheet 61 on the side of thedissolvee metal layer 64 is flattened by having the insulating film 87buried in the gaps in the conductor pattern 55, adhesion with theadhesive 54 on the insulating base material 51 can be made stronger,thereby enhancing adhesive strength.

Subsequently, as shown in FIG. 10A, a step of housing a semiconductorchip 56 inside the void section 52 of the insulating base material 51,and of bonding bumps 57 formed on the active surface thereof to theconductor pattern 55 is performed.

After the semiconductor chip 56 is bonded to the conductor pattern 55,epoxy resin, for example, is injected into the void section 52, therebyforming an underfill resin layer 58 between the conductor pattern 55 andthe semiconductor chip 56. Thus, the conductor pattern 55 is supportedby both the transfer sheet 61 and the underfill resin layer 58.

In addition, since the bumps of the semiconductor chip 56 are formedwith gold or with gold plating on their surfaces, by forming a metalplating of a Sn metal or a Ni/Au metal on the surface of the conductorpattern 55 of copper, chip mounting under low temperature and low loadenvironments may be realized.

In this case, in the present embodiment, since the insulating film 87 isburied between the conductor pattern 55 and the conductor pattern 55, abridge phenomenon across the pattern due to isotropic growth of themetal plating can be prevented.

In addition, by soft-etching the area corresponding to the chipconnection land on the conductor pattern 55 prior to the formation ofthe metal plating, it is effective in that the flatness of the transfersurface will not be compromised by the formation of the metal plating.

Next, the transfer sheet 61 is removed. The removal of the transfersheet 61 is comprised of a step of separating and removing the metalbase material 62 from the dissolvee metal layer 64 (FIG. 10B), and astep of dissolving and removing the dissolvee metal layer 64 (FIG. 10C).

Since this step of removing the transfer sheet 61 is performed through amethod similar to the method described in the first embodiment above, adescription thereof will herein be omitted.

After the removal of the transfer sheet 61 is completed, as shown inFIG. 10D, a step of filling the through-holes 53 of the insulating basematerial 51 with an electrically conductive material 59 as anelectrically conductive material through screen printing or a dispensingmethod, while covering the surface of the conductor pattern 55, exceptfor parts corresponding to areas where the through-holes 53 are formed,with a solder resist 60 is performed.

Thus, a device-incorporated substrate 50′ of the present embodiment isproduced.

According to the present embodiment, advantages similar to those of thefirst embodiment described above can be obtained.

In particular, according to the present embodiment, since the conductorpattern 55 can be bonded to the insulating base material 51 with highadhesion strength, it is possible to obtain the device-incorporatedsubstrate 50′ that is superior in durability.

In addition, in cases where a metal plating is formed in the chipmounting area of the conductor pattern 55, since short circuiting withinthe pattern can be prevented, it is possible to accommodate the mountingof semiconductor chips having a narrow pad pitch.

Fourth Embodiment

Next, FIG. 11A through FIG. 11F show the fourth embodiment of thepresent invention. In the present embodiment, a method of manufacturinga device-incorporated substrate related to the present invention will bedescribed. It is to be noted that, in the drawings, the same referencenumerals are given to parts that have correspondence in the firstembodiment described above, and detailed descriptions thereof will beomitted.

In the present embodiment, a plating resist 72A (FIG. 11B) forelectroplating formed when depositing a conductor pattern 55 on thesurface of a transfer sheet 61, shown in FIG. 11A, on the side of adissolvee metal layer 64 is configured as the insulating film 87 forflattening described in the third embodiment above.

The plating resist 72A is such that, at the time of forming theconductor pattern 55, the gaps in the conductor pattern 55 are filled asshown in FIG. 11C.

Therefore, after the conductor pattern 55 is formed, it becomes possibleto adhere it onto an insulating base material 51, as shown in FIG. 11D,without having to separately form an insulating film for flattening, andthus, advantages similar to those of the third embodiment describedabove can be obtained.

In addition, by using a material having adhesiveness for the platingresist 72A, it is possible to adhere the conductor pattern 55 onto theinsulating base material 51 with higher bonding strength.

In addition, in this case, if the wiring density of the conductorpattern 55 is relatively low, it is possible to do without an adhesive54 on the insulating base material 51.

Since the chip mounting process (FIG. 11E) and the process of removingthe transfer sheet (FIG. 11F) after adhering the conductor pattern 55are similar to those of the first embodiment described above,descriptions thereof will herein be omitted.

Hereinabove, embodiments of the present invention have been described,however, the present invention is by no means limited thereto, andvarious modifications are possible based on the technical spirit of thepresent invention.

For example, in the respective embodiments above, the transfer sheets 61and 91 were configured, as shown in FIG. 5A, with the electricallyconductive adhesive resin layer 63 lying between the metal basematerials 62 and 92 and the dissolvee metal layers 64 and 94 so as tomake the metal base materials 62 and 92 and the dissolvee metal layers64 and 94 separable from each other, but the configuration of thetransfer sheets 61 and 91 are not limited thereto, and so long as theconfiguration allows for the separation of the metal base material andthe dissolvee metal layer from each other, any configuration may beadopted.

For example, a transfer sheet 101, whose sectional structure is shown inFIG. 5B, is configured with an intermediate layer 103 of chromiumplating lying between a metal base material 102 of copper and adissolvee metal layer 104 of nickel plating, and in such a manner thatthe dissolvee metal layer (Ni) 104 and the intermediate layer (Cr) 103are separated at the interface making use of the plating stressdifference. In the step of melting and removing the dissolvee metallayer (Ni) 104 after the metal base material 102 and the intermediatelayer 103 have been removed, if the conductor pattern to be transferredis copper, a sulfated hydrogen peroxide etching solution, for example,may be used.

In addition, in FIG. 5B, if the intermediate layer 103 and the dissolveemetal layer 104 are formed of chromium plating and nickel-cobalt alloyplating, respectively, each of the layers 103 and 104 can be easilyseparated at the interface thereof. In this case, in the step ofdissolving and removing the dissolvee metal layer (Ni/Co) 104, if theconductor pattern to be transferred is copper, a soft-etching agent witha sulfated hydrogen peroxide solution base, for example, may be used.

In addition, in each of the embodiment above, examples in which theremoval of the transfer sheets 61 and 91 are comprised of the step ofseparating and removing the metal base materials 62 and 92, and the stepof dissolving and removing the dissolvee metal layer 64 and 94 weredescribed, however, instead, the transfer sheet as a whole may bedissolved and removed. In this case, the transfer sheet may be comprisedof similar metals, or it may be comprised of a layered body ofdissimilar metals. In particular, in the latter case, each metal layermay be selectively etched using different etching solutions.

For example, FIG. 5C shows the configuration of a transfer sheet 111comprised of first and second metal layers 112 and 114 that aredifferent from each other. Here, assuming the first metal layer 112 iscopper and that the second metal layer 114 is nickel, by using analkaline etchant, it is possible to etch just the first metal layer (Cu)112. Similarly, if the first metal layer 112 is copper and the secondmetal layer 114 is aluminum, by using a warm sulfuric acid solution asan etching solution, it is possible to etch just the first metal layer(Cu) 112. Other combination examples for the first and second metallayers 112 and 114 include nickel and gold, copper and chromium, and thelike.

In addition, these combination examples of dissimilar metals can also beapplied as combination examples between the metal constituting thedissolvee metal layer (64, 94) and the metal constituting the conductorpattern (55, 85).

Further, the transfer sheet may be comprised of two layers, the metalbase layer and the dissolvee metal layer, and each of these layers maybe separated by way of the difference in the thermal expansioncoefficient between each layer. Alternatively, as in a transfer sheet121 shown in FIG. 5D, a heat foaming layer 123 may be placed between ametal base layer 122 and a dissolvee metal layer 124, and the metal baselayer 122 and the dissolvee metal layer 124 may be separated by foamingthe heat foaming layer 123 through a process of heating it to apredetermined temperature.

As described above, according to a method for manufacturing adevice-incorporated substrate and a method for manufacturing a printedcircuit board of the present invention, since a metallic sheet is usedfor the transfer sheet, it is possible to form a fine-pitch conductorpattern with high precision, and it is also possible to transfer theformed conductor pattern to an insulating layer while ensuringdimensional stability. In addition, because the removal of the transfersheet is ultimately carried out by dissolving and removing the transfersheet, it is possible to ensure a proper transfer process for theconductor pattern.

In addition, because the transfer sheet includes a metal base materialand a dissolvee metal layer that is layered so as to be separable withrespect to the metal base material, and because the removal of thistransfer sheet is comprised of a step of separating and removing themetal base material from the dissolvee metal layer and a step ofdissolving and removing the dissolvee metal layer, the cost, in terms oftime, required for the step of removing the transfer sheet is reduced,and an improvement in productivity can be expected.

Further, according to a device-incorporated substrate and a printedcircuit board of the present invention, since the conductor patternformed on the insulating layer is comprised of an electroplated layer,the conductor pattern can be made finer in pitch, and packaging densitycan be improved.

The invention claimed is:
 1. A method for manufacturing adevice-incorporated substrate having an insulating layer, a conductorpattern thereon, a void section formed therein, and an electric devicehoused in said void section and connected to said conductor pattern,said method comprising: providing an insulating layer; a void sectionforming step of forming a void section in said insulating layer;providing a transfer sheet comprising a metallic base and a dissolveemetal layer over the metallic base, the transfer sheet being formedseparate from, and un-connected to, said insulating layer; a patternforming step of forming a conductor pattern over one surface of saidtransfer sheet, wherein the conductor pattern is formed by a platingprocess; a pattern transfer step of adhering said transfer sheet andsaid insulating layer to each other with said conductor patterntherebetween; a transfer sheet removal step for removing said transfersheet from at least said conductor pattern; a device housing step ofhousing said electric device within said void section, with saidelectric device connected to said conductor pattern, the device housingstep occurring after the pattern transfer step and before the transfersheet removal step; and wherein neither the metallic base nor thedissolvee metal layer of the transfer sheet is removed prior to saidtransfer sheet removal step, and said transfer sheet removal stepincludes dissolving and removing at least a part of said transfer sheet,including at least the dissolvee metal layer, and wherein said patterntransfer step occurs after said pattern forming step, and said transfersheet removal step occurs after said pattern transfer step,characterized in that: an adhesive material is applied onto one surfaceof said insulating layer in advance in said pattern transfer step. 2.The method for manufacturing a device-incorporated substrate asdescribed in claim 1, characterized in that: removal of said transfersheet during said transfer sheet removal step includes dissolving thedissolvee metal layer.
 3. The method for manufacturing adevice-incorporated substrate as described in claim 1, characterized inthat: said pattern forming step is done by an electroplating method. 4.The method for manufacturing a device-incorporated substrate asdescribed in claim 1, characterized in that: said pattern forming stepincludes a step of, after said conductor pattern forming step, buryingan insulating material in gaps in said formed conductor pattern andsubsequently flattening the surface of said transfer sheet such that thesurfaces of the conductor pattern and the insulating material aresubstantially flush.
 5. The method for manufacturing adevice-incorporated substrate as described in claim 1, characterized inthat: said device housing step includes a step of adhering said transfersheet and said insulating layer to each other, and thereafter housingsaid electric device into said void section and connecting said electricdevice to said conductor pattern.
 6. The method for manufacturing adevice-incorporated substrate as described in claim 2, characterized inthat: said dissolvee metal layer and said conductor pattern are made ofdifferent metal material, and said step of dissolving and removing saiddissolvee metal layer is done by using an etchant which is able todissolve said dissolvee metal layer but is unable to dissolve saidconductor pattern.
 7. The method for manufacturing a device-incorporatedsubstrate as described in claim 1, characterized in that: said voidsection forming step includes a step of forming a through hole togetherwith said void section, for connecting both surfaces of said insulatinglayer, and a step of filling conductive material into said through hole.8. The method for manufacturing a device-incorporated substrate asdescribed in claim 7, said method characterized by further comprising:layering multiple ones of each of said formed device-incorporatedsubstrates with electric connections formed via said filled throughholes.
 9. The method for manufacturing a device-incorporated substrateas described in claim 2, characterized in that said transfer sheetfurther comprises an adhesive resin formed between said metallic baseand said dissolvee metal layer.
 10. The method for manufacturing adevice-incorporated substrate as described in claim 1, characterized inthat said transfer sheet is at least 100 μm thick in order to providerigidity to the transfer sheet.
 11. The method for manufacturing adevice-incorporated substrate as described in claim 2, characterized inthat said dissolvee metal layer is formed to a thickness of 5 μm orless.
 12. The method for manufacturing a device-incorporated substrateas described in claim 2, characterized in that said transfer sheetfurther comprises a heat foaming layer formed between said metallic baseand said dissolvee metal layer.
 13. The method for manufacturing adevice-incorporated substrate as described in claim 2, characterized inthat said transfer sheet removal step further comprises a step ofremoving said metal base by a physical process prior to removing saiddissolvee metal layer by said dissolving process.